Le 31 janv. 08 à 15:09, Andrej Bauer a écrit :

> I have become to prefer option types as return values (as opposed to  
> exceptions), but I admit it can be annoying to always consider both  
> possibilities, especially if you know that "None" won't happen.

Maybe it is a point of view, you are fed up of considering both  
possibilites while I'm personally fed up of writing

match try Some (f x) with e -> None with
| None -> ..
| Some v -> ...

Because I need tail recursive functions.

> If the library only provides "find" that returns an option type, the  
> above solution gets around constant checking. But how much runtime  
> overhead does it cause? Has anyone measured that?

No idea. Unscientific benchmark at the end of the email.

> What is wrong with having two functions?

You have to choose. You don't have exceptionless error mangement  
anymore which is the point of the proposal. As the module developer I  
don't want to write two functions to do the same thing albeit in a  
slight different way one of which strikes me as the being the wrong way.

Best,

Daniel

osx 10.5.1 1ghz G4 512 ram

 > cat in.ml
let () =
   let f = ref [] in
   try while (true) do f := (input_line stdin) :: !f done
   with End_of_file -> ignore (!f)

 > cat inb.ml
let () =
   let rec next acc =
     match try Some (input_line stdin) with End_of_file -> None with
     | None -> acc
     | Some l -> next (l :: acc)
   in
   ignore (next [])

 > ocamlbuild in.native inb.native
Finished, 8 targets (0 cached) in 00:00:01.

 > time jot 1000000 | ./in.native

real	0m4.814s
user	0m4.371s
sys	0m0.218s

 > time jot 1000000 | ./inb.native

real	0m4.790s
user	0m4.355s
sys	0m0.217s